Spark quenching arrangement



June 25, 1940. w. sAvlLLE 2,205,602

4 SPARK Qunucnnle ARRANGEHENT l Filed larch 26, 1938 2 Shee'cg--SheetI 1 msumrme WASHER 5 H INVEA/Top w/LL/E SAV/LL;

June 25, 1940. w. 5AV|LLE 2,205,602

SPARK QUENCHING ARRANGEMENT Filed March 26, 1938 2 Sheets-Sheet 2 METAL `SFWAYED ,l I3

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Patented June 25, 1940 2,205,602 SPARK QUENCHING ARRANGEMENT Willie Saville, Huyton, Liverpool, England, as-

signor to Associated Telephone & Telegraph Company, Chicago, Ill.,

Ware

'Application March 26, 1938, Serial N0. 198,182

. In Great Britain April 6, 1937 :4 Claims. (Cl. F15-294) plurality of circuits are connected for common spark-quenching arrangement.

Fig. 4 diagrammatically illus having the common spark-quenching *arrangement of Fig. 3.

Fig. 5 shows a .Thyrite d Fig. 6 is a cross. section taken on the line The present invention relates to spark quenching arrangements for use in telephone or like systems and isparticularly concerned with -the prevention of destructive arcing at points where 5 highly inductive circuits are suddenly or repeatedly opened, for instance in connection with the control .or operation of step-by-step automatic switches which are electromagnetically driven. f

l Hitherto reduction of arcing in such circumstances has generally been eiiected by the use of condensers and resistances of suitable value connected in series across the contacts opening the circuit or alternatively connected across the 15 source .of energy producing the arc.

Good results have been achieved by this method for many years but it has the disadvantage that the assemblage of condensers and resistances is somewhat costly where a large number of quencha0 ing circuits are required and also a good deal of mounting space is taken up. The object of the invention is to provide spark quenching facili! 'ties by means involving a considerable reduction in cost and also an appreciable saving in mounting space.

According to the invention use is made of a Asolid body composed of material the resistance of which is substantially the same for both directions of current ilow but which decreases with 80 increase of voltage. Material of this type may be considered as substantiallyA Aan insulator as long as the applied voltage does not exceed a critical value but when it is subjected to a higher voltage it breaks down momentarily and passes -I quite a considerable current. Thismaterial is thus very well suited to the absorption of high inductive voltages which would otherwise produce sparking.

, One material having these properties com- 40 prises a. mixture of silicon carbide with carbon and/or tungsten or molybdenum which is agglomerated under pressure and subsequently baked, the resulting mass'having a resistancecurrent characteristic which is substantially 4l hyperbolic. This material is commercially known as Thyrite.

The invention will be more fully understood from the following description of two methods of carrying it into effect which should'be taken in I0 conjunction with4 the accompanying 'drawings comprising Figs. 17.

Fig. 1 shows a spring pile-up using a 'Ihyrite" washer to separate the interrupter springs.

Fig. 2 shows a top view of Fig. 1. Fig. 3 shows a disc of Thyrite to which a a corporation of Delatrates the circuits isc having ridges.

. Fig. 7 shows another Thyrite disc having metal-sprayed spots von one of its surfaces for circuit connections.

One known method in the use of VThyrite is shown in the -Siegmund Patent 2,052,318, issued August 25, 1936 wherein Thyrite is made into a washer of suitable shape and thickness and is mounted in a spring pile-up between a pair of cooperating contact springs. An arrangement of interrupter springs separated by a Thyrite washer is shown in Figs. 1 and 2 which represent a side elevationand a plan respectively and indicate the arrangement used in a known type of vautomatic switch. Of the various components which are held together by the bolts I the top spring 2 is the driving spring for' the switch wipers and is stressed by the movement of the magnet armature by means of a lever engaging it near its left-hand extremity. Springs 3 and 4 are the actual interrupter springs and spring 3 is of substantially the same shape as spring 2 and is arranged to be engaged near its left-hand end by a further member operated by the armature so as to open the interrupter contacts when the magnet is fully operated. The lower spring 4 is provided with a soldering tag 6 and a side extension 'I carrying the appropriate contact point. The lowermost member 8 of the pile is conveniently made of a double wedge shape as shown so as to permit adjustment by suitable operation of bolts l. The various members of apart and electrically insulated by insulating washers 9 but the member I0 which in the ordinary construction would also be an insulator is in this case made of resistancematerial of substantially rectangular shape corresponding to the upper insulator 9. In this case good electrical contact is preferably lsecured by metal spraying both surfaces of the Thyrite washer the assembly are kept would permit some altera normal substation circuit since this is ranged so as to give a spark quenching effect at the dial switch contacts.

According to the invention it is more convenient to mount the spark absorbing material remote from the interrupter springs and it is proposed that the same unit shall be arranged to quench sparks from afplurality of separate circuits. For example the preferred arrangement shown in Figs. 3 and 4 might be adopted in which the Washer made of 'Ihyrite" is pressed into the form of a circular disc about the size of a shilling and one surface, the lower surface in Fig. 3, is completely metal-sprayed to form a common connecting point. The upper surface is sprayed as shown at a plurality of disconnected points Il, eight in number, which are equally spaced round the circumference of the disc. This enables eight ciri cuits to be quenched from the same disc, connections being made by way of the individual leads I2 extending to the separate points and the common lead I3 extendingtothe lower surface. These circuits are shownin detail in Fig. 4 wherein 22, 32 and 42' indicate relays or magnets each having an inductive winding with one terminal connected to the negative pole of battery B and the opposite terminals each connected by a conductor I2 to a separate metal sprayed spot |I on the Thyrite disc. Each conductor I2 is connected to a spring contact which cooperates with an aslsociated spring contact such as shown. at 2|, 3|

and 4I. The bottom of the "'I'hyrite disc is `metal sprayed at II and is connected by wayof conductor I3 to lground. The battery B is a common battery and has its positive pole grounded. In Figs. 5 and 7 the metal sprayed spots II are connected to inductive circuits (not shown) identical to the circuits shown in Fig. 4.

Assuming now that contacts 2| are closed and that the winding-of relay or magnet 22 is enercharge gized over its obvious circuit and that shortly thereafter contacts 2| open. inductive, an abnormal-increase in voltage or inductive discharge takes place when contacts 2| open. In ordinary circuits vthis inductive diswould be dissipated in the form of a spark at contacts 2| but inthis case an inductive discharge path has been provided by way of c nductor I2, metal sprayed spot the Thyrite disc,.the metal sprayed bottom ||,`and byway of conductor I3 to ground. Since this inductive discharge current has a considerably higher volt--v age than the normal voltage of battery B and also since this inductive discharge current exceeds the critical value, the Thyrite disc, insulating qualities break down and the inductive discharge current passes ythru the""I'hyrite disc and over conductor I3 to ground'instead of sparking thru the ,open contacts 2| to ground. The other inductive: circuits connected to conductor l2 all operate in the same manner as just described.

From the foregoing description it will be obvious that a single disc of Thyrite, when metal sprayed and connected to a plurality of separate inductive circuits as shown, forms a common Since relay 22 is p1ura1ity or induc- `nections I to prevent leakage .between such spots,

the die for pressing the Thyrite disc could .be arranged to undulate the surface, such as for instance, by the formation of a series of concentric ridges around each spot as shown in Figs. 5 and 6.

As another alternative to increase still further the usefulness of the disc, one or both sides could be metal-sprayed at a plurality of disconnected spots lying around a common connecting spot in the centre as shown in Fig. 7. With this arrangement it will be appreciated that the quenching circuits provided by the disc will be across the surface between the respective spots rather than through the thickness of the material as previously and consequently the minimum thickness is determined by mechanical rather than'electrical considerations. With the dimensions assumed as many as eight or more circuits could readily be quenched through the same piece of material, in which case the 'saving in space becomes an important consideration.

I claim:

`1. In a spark quenching arrangement comprising a plurality of inductive circuits, a single body of material the resistance of which is substantially the same for both directions of current flow but which decreases with increase of voltage, and individual and separate connecting means connecting each said circuit to said singlebody, and

means whereby said single body in combination in claim 1 in which said single body comprises a disc and each said connecting means is indi' vidually and separately connected to one side of said disc while the opposite side of said disc is connected to ground so that the inductive discharge current flows through the material of said/ disc.

3. A spark quenching arrangement as claimed in claim 1 in which said single body is in the form of a disc and a common ground connection is made to one side of said disc while each said individual circuit connecting means is` individually connected to an individual point on theother side of said disc.

4. A spark quenching arrangement as claimed in claim 1 in which a common ground connection in combination with said individual connecting means are all individually connected to one surface of said body so that current due to theinductive voltage flows substantially along the surface of the material of said body.

WILLIE SAVILLE. 

